A photocathode device is a vacuum electronics device that emits a beam of electrons when photons from a suitable light source (e.g., lasers, high intensity Light Emitting Diodes (LEDs), etc.) impinge on its photoemissive coating in a vacuum environment with a photon energy that exceeds the work function of the photocathode device. Photocathode devices can produce high peak and high average current densities while also allowing a precise gating of the photoemission of the electron beam. A photocathode device is often characterized by its Quantum Efficiency (QE), which is the ratio of the number of photons incident on the photoemissive coating to the number of emitted electrons. QE values for photocathode devices used with a Radio Frequency (RF) accelerator, for example, are typically about 2-10%.
A problem that that limits the utility of photocathode devices for continuous operation relates to evaporation and/or desorption of the photoemissive coating during photoemission. This degradation problem limits the potential use of photocathode devices as electron sources for medical x-ray devices, for high power devices (e.g., free electron lasers), and for other devices in which continuous operation over a period of at least a few weeks versus a few hours is desirable. Accordingly, an improved photocathode device may be beneficial to metrics of a given application, such as reduced cost, reduced system complexity, and/or improved performance.